Electric machines having a rotor and a stator according to the prior art serve to drive aggregate units or vehicles. In such cases, the stator is situated in an enclosing jacket, which also serves to hold and stabilize the stator. Dissipation heat develops, due in part to induced electric circular currents in the electrically conductive elements of the electric machine. This causes the rotor and stator of the electric machine to heat up, which results in a reduction of the performance of the electric machine. However, the aforementioned jacket has the disadvantage here that the dissipation of heat from the stator is impeded by the jacket.
Cooling systems for electric machines have therefore been developed, such as for example a liquid cooling system in which a liquid coolant flows through a cooling jacket and thereby cools the rotor and the stator. The delivery of liquid to the rotor normally takes place through the axle of the rotor, while the delivery of liquid to the stator normally takes place through a pipe or hose line fed in axially or radially. The liquid coolant is thereby conveyed through the stator and through the rotor, where it is warmed, and is then cooled down again outside the electric machine by means of a cooling radiator cooled, for example, by air. The liquid cooling system thus requires significant construction effort and expense, and not inconsiderable operating costs for the liquid cooling system.
Air cooling systems have also become known in which cooling ribs are provided on the outer jacket so as to enlarge the surface, enabling cooling air to be conveyed along the jacket in order to cool the jacket by the cooling air. The jacket represents a significant heat resistance in this case; however, such that the temperature of the electric machine still leaves something to be desired.
An electric machine has become known through EP 1 432 102 A2 in which so-called heat pipes are used to carry heat away from the gap between rotor and stator and to a cooling radiator. This configuration requires substantial construction space.